1. Field of the Invention
The present invention relates to a drying method of a substrate surface and a supporting fixture of the substrate used in the drying method. More particularly, the invention relates to a drying method of the substrate surface, which permits achievement of a satisfactory dried state, even for the proximity of the contact portion of the substrate with a carrier holding section for holding and conveying the substrate, during the drying process carried out after a liquid treatment of a semiconductor wafer or a liquid crystal substrate, and a supporting fixture of the substrate using such a method.
2. Description of the Related Art
Conventional drying methods of a substrate surface after cleaning thereof in the manufacturing process of a semiconductor wafer or a liquid crystal substrate are broadly classified into the sheet-feed treating method and the batch treating method. The sheet-feed treating method mainly comprises the steps of rotating the substrate, removing water while flicking water from the substrate surface by use of the centrifugal force of rotation, and drying the same in a nitrogen atmosphere or a vacuum atmosphere. This method has, as compared with the batch treating method, problems of a low throughput (quantity of handled work per unit time), and easy occurrence of water mark (trace of evaporated water) on the substrate surface. To avoid these inconveniences, therefore, a batch-type drying treatment of the substrate surface is applied in many cases after cleaning through as dipping treatment of the substrate. For example, Chapter 6 of the xe2x80x9cPresent Status and Problems of Wafer Cleaning Technologyxe2x80x9d published by Realize Publishing Co., in May 2000 reports a batch-type drying method in combination with a dipping treating method which permits minimization of occurrence of water marks and adhesion of particles. As typical examples of the drying method, the above-mentioned article reports isopropyl alcohol (IPA) evaporation drying, direct substitution drying, Marangoni drying, and vacuum drying. In the above-mentioned methods, water drops on the substrate are dripped off by gravity for drying by relatively lowering the liquid level relative to the substrate having been dipped in the treatment liquid in the treatment vessel, although these methods use different kinds of drying gas.
In any of the aforementioned drying methods, a satisfactory dried state is available for the portion of the substrate surface distant from the substrate holding section of the carrier (hereinafter referred to as the xe2x80x9ccarrier holding sectionxe2x80x9d) for holding and conveying the substrate in the treatment vessel. However, defective drying occurs particularly at the contact portion of the substrate surface with the carrier holding section, and occurrence of water markers or adhesion of particles may sometimes be observed. The above-mentioned publication contains no description about occurrence of defective drying of the substrate surface near the carrier holding section for holding a semiconductor wafer or a liquid crystal substrate, or the necessity to prevent the same, and does not describe a method for solving such problems.
Typical examples of cleaning treatments of the substrate include etching, photoresist stripping and cleaning prior to diffusion. In any case, even when cleaning with a treatment solution is satisfactorily accomplished, occurrence of water marks or adhesion of particles, if any, in the drying treatment that follows causes a decrease in product yield. As a counter-measure against defective drying of the substrate surface tending to easily occur particularly near the carrier holding section described above, it is the common practice to exclude portions suffering from occurrence of water marks or adhesion of particles and thus to perfect commercial products by increasing edge-cut portions of the semiconductor wafer or the liquid crystal substrate, i.e., increasing rejected portions on the outer periphery of the substrate not perfected into commercial products. This causes a decrease in the number of available products per semiconductor wafer or liquid crystal substrate. It is also conceivable to improve draining and to reduce defective drying in the proximity of the carrier holding section by altering the cutting method of the fixing groove of the carrier holding section itself. Control is however difficult because of the difference in surface tension caused by the wafer surface condition.
For example, in the drying methods of a semiconductor substrate disclosed in Japanese Unexamined Patent Application Publications Nos. 1-226157, 3-62521 and 5-74921, it is proposed to dry the substrate surface by reducing the pressure of the entire treatment vessel. However, with this method of reducing the pressure of the entire treatment vessel alone, it is impossible to solve the problem of remaining liquid drops occurring near the carrier holding section of the substrate upon drying the substrate surface while lowering the liquid level. It is therefore inevitable to depend upon evaporation for removal of liquid drops remaining in this portion. This leads to the necessity of a long period of time for drying, resulting in occurrence of water marks. Furthermore, Japanese Unexamined Patent Application Publications Nos. 4-287321, 9-36082, and 10-41267 disclose apparatuses which dry a substrate surface by introducing nitrogen or IPA vapor in the treatment vessel under atmospheric pressure. These publications contain however no description of the problem of defective drying occurring near the carrier holding section of a substrate surface such as a semiconductor wafer surface, and hence nothing about a method for solving these problems.
An object of the present invention is therefore to provide a drying method of a substrate surface, which, in the drying performed after subjecting a semiconductor wafer or a liquid crystal substrate to a chemical dipping and/or water dipping, never causes defective drying of the substrate surface particularly near the carrier holding section, and a supporting fixture of the substrate used in this drying method.
Another object of the present invention is to provide a drying method of a substrate surface excellent in economic merits, which uses facilities conventionally used for drying as they are, and permits improvement of the substrate product yield only by making a simple improvement, and a simple supporting fixture used for such a method.
The aforementioned objects are achieved by the present invention as described below. More specifically, the invention provides a supporting fixture of a substrate used in a drying method of a substrate surface for drying the substrate surface, after subjecting the substrate to a chemical dipping treatment and/or a water dipping treatment, while causing relative descent of the treatment liquid level relative to the substrate, having a supporting rod of which at least the center portion is formed of a porous material; wherein a groove for supporting the substrate on the surface of the supporting rod is provided; the groove is configured so that, when supporting the substrate, the substrate comes into contact with the porous material; and a vacuum mechanism for converting the interior of the supporting rod into a vacuum state is provided.
Preferred embodiments of the above-mentioned supporting fixture of a substrate include a mechanism for purging pores in the portion made of the porous material with a desired gas and/or liquid. Another preferred embodiment is a supporting fixture of a substrate further comprising, together with the vacuum mechanism, a liquid trap vessel, having a vent valve and a drain valve, for trapping the liquid sucked by reducing the pressure. The preferred embodiments of the invention include a supporting fixture of a substrate, wherein the supporting rod has a double structure comprising a core made of a porous material and an outer edge surrounding the core, made of a material not porous; the outer edge comprises a quartz pipe not made porous; and the core comprises a quartz rod sintered to make the same porous. Still another embodiment is a supporting fixture of a substrate, wherein the supporting rod had a double structure comprising a core made of a porous material and an outer edge surrounding the core made of a material not made porous; the outer edge comprises a pipe made of a fluororesin; and the core comprises a fluororesin rod polymerized to make the same porous.
Further another embodiment of the present invention is a drying method of a substrate surface for drying the substrate surface after subjecting the substrate to a chemical dipping treatment and/or a water dipping treatment, while causing relative descent of the treatment liquid level relative to the substrate; comprising the steps of previously installing a supporting fixture of a substrate in a treatment vessel; transferring the substrate held by the carrier holding section onto the groove on the supporting rod surface of the supporting fixture; and drying the substrate surface in this state while reducing the pressure in the interior of the supporting rod.